In certain applications that track the positions or motion of a mobile transmitter or transducer (i.e., tracked device), it would be helpful to provide a simple, economical means to improve tracking accuracies without the need for complicated or costly receiver network setup or calibration procedures. One commonly used method to track the positions of tracked devices is implemented in current wireless networks that track RFID tags in buildings, on campuses and commercial environments. The tracking in said networks is made possible by placing multiple receivers throughout the tracked area. The receivers identify the signals of the tracked device and use signal amplitude levels to determine rough ranges, typically measured in feet or meters, between the tracked devices and the receivers within the signal reception range of the tracked devices. High accuracy cannot be obtained using signal amplitude, and receivers need to be located at positions on a mapped layout of the building, campus, etc.
The kind of signal strength ranging system described above can work well in an environment that does not require high accuracy position detection for the tracked devices or very fast and accurate receiver position calibration. However, in some applications, requirements may be much more demanding with inch or even sub-millimeter accuracy requirements and fast, easy receiver setup for operation.
Certain computer-based virtual reality applications that track the position of a controller (guns in gaming applications, surgical probes in image guided surgery applications, etc.) require high tracking accuracy of the actual position of the tracked device. Since in these virtual reality applications the device would be registered with screen images provided by software, very high position accuracies are required to provide realistic interaction between the user (i.e., tracked device) and the software program. For applications with high accuracy requirements, simple amplitude detection would not be adequate. A signal time of arrival approach for the tracked device tracking can provide higher accuracies but a complicated calibration process or receiver setup would not be practical.